1. Field of the Invention
The present invention relates to a method of manufacturing a rotor assembly, a rotor assembly, and a turbo compressor.
Priority is claimed on Japanese Patent Application No. 2010-074929, filed on Mar. 29, 2010, the content of which is incorporated herein by reference.
2. Description of Related Art
Typically, a turbo compressor that compresses and discharges a gas such as air or a refrigerant gas by rotating an impeller is known (for example, refer to Japanese Unexamined Patent Application, First Publication No. 2007-177695). The impeller is fixed to a rotation shaft, and the rotation shaft is supported by a bearing so as to be rotatable. The rotation shaft and the impeller are rotated by the rotating power of a predetermined driving device (a motor or the like), and as the impeller is rotated, the gas is sent to a diffuser formed at the periphery of the impeller to be compressed.
The impeller, the rotation shaft, and the bearing may be assembled into a rotor assembly before being built in the turbo compressor. In a turbo compressor having two compression stages as disclosed in Japanese Patent Application No. 2007-177695, two impellers are provided on both sides with a predetermined bearing interposed therebetween. In addition, on the opposite side of a rotation shaft to the side to which an impeller is fixed, a pinion gear is molded integrally with a rotation shaft main body. Accordingly, the rotor assembly may be assembled in the order of fitting the bearing to a supporting portion after passing one impeller through the supporting portion of the rotation shaft supported by the bearing and fixing the impeller thereto at a predetermined position.
However, when a long bearing life span needs to be ensured, for example, using a large bearing is considered. In order to use the large bearing, the rotation shaft needs to be of a thickness corresponding to the inside diameter of the bearing. However, as described above, during assembly of the rotor assembly, the one impeller is first passed through the supporting portion of the rotation shaft. Accordingly, it is difficult to use a thick rotation shaft, and thus it is difficult to ensure a long bearing life span using the large bearing.
In order to solve the problems, an object of the invention is to provide a method of manufacturing a rotor assembly, a rotor assembly, and a turbo compressor having the same, capable of ensuring a long bearing life span with the use of a large bearing.
In order to accomplish the object, the invention employs the following apparatus.